Rack and pinion steering gear

ABSTRACT

A rack and pinion steering gear wherein the rack bar is supported in the rack tube by bearing sleeves journalled in the axial open ends of the tube without use of a yoke. In order to provide alignment adjustment, the pinion has at least one end thereof supported in an adjustable eccentrically mounted spherical bearing to allow movement of the pinion with regard to the rack.

Uited States Patent Colletti Aug. 21, 1973 RACK AND PINION STEERING GEAR[75] Inventor: John B. Colletti, Grosse Pointe Park,

Mich.

[52] US. Cl 74/498, 74/396, 74/422 [51] Int. Cl 862d 3/12 [58] Field ofSearch 74/498, 497, 499,

[56] References Cited UNITED STATES PATENTS 1,332,161 2/1920 Dahlen74/498 2,547,784 4/1951 Saives 74/396 X 8/1953 Stallsmith 74/3963,623,379 11/1971 Bradshaw et al. 74/498 FOREIGN PATENTS OR APPLICATIONS613,432 12/1960 Italy 74/498 Primary Examiner-Milton KaufmanAttorney-Carlton Hill, Donald J. Simpson et a1.

[57] ABSTRACT 2 Claims, 5 Drawing Figures RACK AND PINION STEERING GEARBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to steering gear assemblies and more particularly to a rack andpinion steering gear assembly.

2. Prior Art Rack and pinion steering assemblies such as those used tocontrol the attitude of the dirigible wheels of a vehicle have generallyincluded a rack bar mounted for axial movement in a rack tube throughwhich a pinion projects transversely, the pinion teeth engaging theteeth of the rack section of the rack bar. In order to provide forsupport and alignment of the rack and to maintain contact between therack and the pinion, the rack bar was supported at one end of the racktube through a sleeve bushing. The other end of the rack tube normallydid not provide support for the rack bar, the rack bar being contactedby a yoke positioned opposite the pinion to urge the rack bar againstthe pinion. Therefore, support for the rack bar constituted the sleevebushing on one end of the rack tube and the pinion-yoke contactintermediate the ends of the tube. This provided a moment arm forbending forces between the end of the rack bar unsupported by a sleevebushing and the pinion.

When road loads occurred in certain situations, the bending momentapplied to the rack at that length would have to be absorbed by the yokebearing in the one direction and by the pinion in the other direction.When such loads were sufficient, damage to one or the other of thecomponents could occur.

SUMMARY OF THE INVENTION My invention overcomes the above disadvantageof the prior art by providing a sleeve bushing at either end of the racktube so that the rack bar is supported independent of the pinion. Theneed for a yoke is eliminated.

In order to provide for adjustability of the pinion with regard to theteeth of the rack, which adjustability is necessary because of thesupport of the rack at both ends of the rack tube, 1 mount at least oneend of the pinion in a spherical bearing which is supportedeccentrically in a housing which constitutes the rack tube and thepinion housing. The eccentric mount allows for movement of the piniontowards and away from the rack in such a manner as to provide at thesame time a minimal movement parallel to the rack.

It is therefore an object of this invention to provide an improved rackand pinion steering gear assembly.

It is another object of this invention to provide a rack and pinionsteering gear assembly which eliminates the need for a yoke.

It is a further and more specific object of this invention to provide arack and pinion steering gear assembly wherein the rack is supported atopposite ends of the rack bar by bushings.

It is yet another and more specific object of this invention to providea rack and pinion steering gear assembly wherein the pinion isadjustably received in the housing.

It is a specific object of this invention to provide a rack and pinionsteering gear assembly wherein the rack bar is supported at either endsof the rack tube in bushings and the pinion is adjustably supported inthe rack tube housing by means of an eccentric mount of one end of thepinion.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantagesof the invention will be readily apparent from the following descriptionof certain preferred embodiments thereof, taken in conjunction with theaccompanying drawings, although variations and modifications may beeffected without departing from the spirit and scope of the novel-concepts of the disclosure, and in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a typicalprior art rack and pinion steering gear assembly 10. The assemblyincludes a rack bar 11 having axial ends 12 and 13 to which are attachedtie rods 14 and 15. The tie rods are attached to the axial ends througharticulatable joints 16 and 17, which allow movement of the tie rodswith respect to the rack bar as is illustrated at 14a. The tie rods mayterminate in ball joints 18 for attachment to the dirigible wheels ofthe vehicle. The rack bar, intermediate its ends, is received axiallythrough a rack tube 20 which has a housing bulge portion 21 thereinadjacent to one end 22 of the rack tube. The other end 23 of the racktube 20 is spaced from the housing bulge 21 and contains a sleevebushing or bearing 24 which surrounds the rack bar 11 and supports it inthe open end 23 of the rack tube 20. Normally both the open end 23 andthe rack bar are circular as is the bushing 24.

The housing bulge 21 includes an upper bulge 30 and a lower bulge 31.The lower bulge receives, transversely of the rack tube, a pinion 32having outer diameter teeth 33 thereon. The rack bar contains a toothedsection or rack 34, the teeth of which intermesh with the teeth of thepinion. Therefore, when the pinion is rotated, the rack is movedlaterally, causing a shifting of the tie rods. In order to support therack bar in the rack tube and to assure a contact between the rack teethand the pinion teeth, a yoke 35 is positioned in the upper bulge portion30 and is urged, as by means of a spring 36, against the surface of therack bar opposite the rack. Normally the yoke 35 is positioned oppositethe pinion.

The yoke holds the rack against the pinion and is usually adjusted to apredetermined clearance. Therefore, the rack bar is positioned in therack tube and maintained in axial position therein by a supportconstituting the sleeve bushing 24 and the pinion 32 and yoke 35.

In such prior art steering systems. because the support for the rack barwas positioned at the pinion and yoke. a bending moment arm existsbetween the end 13 of the rack bar and the support point of the pinionand yoke. This distance A. although subject to change with movement ofthe rack bar, can be large enough to disadvantageously affect thestability of the system. At times, the pressure can be great enough todamage portions of the system. Additionally, a non-desirable function isimposed on the pinion in that it becomes a loadbearing point whichrequires additional and costly design criteria for the pinion andhousing support therefor.

Since the tie rods l4, are free to articulate, as is illustrated at 14a,when road loads occur with the tie rod at an angle to the rack, thebending moment is applied to the rack at the length A. This load must beabsorbed either by the yoke in one direction or by' the pinion in theother direction. The direction of the load is a function of both thecause of the load, as for example, wheel shocks encountered upondropping of the wheel into a hole in the road, and thereafter joltingout of the hole, and the attitude of the wheels at the time of theapplication of the load and the position of the tie rod with respect tothe wheel. The design of typical prior art assemblies as illustrated inFIG. 1 had to take all of these factors into consideration in designingthe support for the pinion and the placement and strength of the yoke.

My invention, on the other hand, as best illustrated in FIG. 2,eliminates the use of the yoke and further eliminates the use of thepinion as a bearing member.

As illustrated in FIG. 2, the rack bar is received in a rack tube 51having axial ends 52 and 53. Each of the axial ends 52,53 containstherein a sleeve bushing 54 providing the support for the rack bar.Thus, the rack bar 50 is supported by the rack tube at either end of therack tube in the bushings 54. The pinion 55 is positioned below the rack56 and is received in a bulge portion 57 of the rack tube housing.Because the axial end 58 of the rack bar 50 closest to the pinion is supported by the bushing 54 rather than by the pinion, the bending momentarm mentioned above has a length B as opposed to the greater length A ofthe prior art steering linkages as illustrated in FIG. 1.

A yoke such as the yoke 35 of the prior art linkages functions tomaintain the rack teeth in mesh with the pinion teeth. Because the yokehas been eliminated in my steering gear assembly, I have mounted thepinion in such a way that it can be moved with respect to the rack so asto allow it to be adjusted to intermesh correctly. The pinion 55 isreceived interiorly of the bulge portion 57 of the rack tube housingperpendicular to the axis of the rack bar 51. The housing has twoopenings 59,60 at either end of the bulge area axially of the pinion asillustrated in FIG. 3. The stem 62 of the pinion projects through theopening 59 and an opposite end portion 64 of the pinion terminatesadjacent the open end of the housing. The toothed area 65 of the pinionis positioned intermediate the ends and is aligned with the rack barwhereby the rack straddles the toothed area of the pinion. Sphericalbearings and 71 are received around the shaft 62 and the cylindricalextension 64a projecting from the toothed area to the end 64. Thespherical bearing 70, in the illustrated embodiment, is received in aspherical inner diameter housing member 73 whereby the arcuately curvedinner diameter of the housing member 73 mates with the arcuately curvedouter diameter of the spherical bearing member 70. The housing member'73 is snugly received in the housing 57 adjacent the opening 59 andsupports the shaft 62.

The spherical bearing member 71 is received in a bearing housing member72, which has a mating configured opening 75 which is arcuately curvedto receive the spherical bearing 71. The opening 75 is positioned offcenter in the bearing housing member 72. That is to say that the axis ofthe opening 75 is not the axis of the opening in the housing in whichthe disc-shaped bearing housing member 72 is received. The bearinghousing member 72 is received in a circular inner cavity area 78 of thehousing 57 and is maintained therein as by means'of an outer diameterthreaded nut 74.

In FIG. 4, the axial centerpoint of the bearing housing member 72 and ofthe opening 78 in which it is received is indicated at 80. The axialcenterpoint of the opening 75 in the spherical bearing housing member 72is indicated at 81. The difference between the two, or the amount ofeccentricity, is indicated at 82.

In the preferred embodiment, the eccentric distance 82 is alignedparallel to the centerline of the rack 51 when the assembly ismanufactured.

By aligning the eccentric distance parallel with the centerline,adjustment of the pinion with respect to the rack can be accomplishedmerely by rotating the spherical bearing mounting housing 72 a slightamount in the opening 78. This rotation produces a maximum movement ofthe pinion towards the rack with a minimum movement of the pinionparallel to the rack, which could result in mismatch of the pinion teethto rack teeth. This is illustrated diagrammatically in FIG. 5, whereinthe axial centerline of the spherical bearing mounting housing 72 isindicated at 80, and the assembled centerline of the opening 75 isindicated at 81. It can be seen that by rotating the mounting member 72,the centerline, of the pinion will be moved towards the rack by thedistance C where it is moved parallel to the rack only by the distanceD, the rack centerline being indicated at 90. It is to be understoodthat one or both of the bearings may be adjustable and that thespherical bearings illustrated may be different as by way of example,they may be the outer member of a ball bearing assembly.

It can therefore be seen from the above that my invention provides arack and pinion steering gear assembly wherein the rack is supported inthe rack tube by bushings positioned at the ends of the rack tube, therack being prevented from movement other than axial with respect to thetube and the pinion being adjustably mounted in spherical bearingswhereby it can be moved towards and away from the rack.

Although the teachings of my invention have herein been discussed withreference to specific theories and embodiments and although illustrativemeans for accomplishing explained results have been described, it is tobe understood that these are by way of illustration only and that othersmay wish to utilize my invention in different designs or applications.

I claim as my invention:

1. A rack and pinion steering wheel assembly comprising a rack housing,said rack housing having spaced-apart open axial ends, a rack tubeprojecting through said housing axially thereof and projecting be yondthe axial ends, bushings received in the housing adjacent the axial endsthereof, the bushings slidably supporting the rack bar in the housing, apinion projecting transversely of said rack bar through said housing,means attached to said housing transversely of said rack bar on bothsides of said rack bar rotatably supporting said pinion in said housing,said pinion having teeth intermeshing with the rack bar, said meanssupporting said pinion including bearings on both sides of said rack barsupporting said pinion, at least one of said bearings eccentricallymounted in said housing, the eccentric distance between the centerlineof the one bearing and the centerline of the pinion lying in a planeparallel to the centerline of the rack, the eccentrically mountedbearing being a spherical bearing having a spherical outer surfacereceived in an opening in a mounting member, said mounting member havinga cylindrical outer diameter surface rotatably received in a one of saidbearings.

1. A rack and pinion steering wheel assembly comprising a rack housing,said rack housing having spaced-apart open axial ends, a rack tubeprojecting through said housing axially thereof and projecting beyondthe axial ends, bushings received in the housing adjacent the axial endsthereof, the bushings slidably supporting the rack bar in the housing, apinion projecting transversely of said rack bar through said housing,means attached to said housing transversely of said rack bar on bothsides of said rack bar rotatably supporting said pinion in said housing,said pinion having teeth intermeshing with the rack bar, said meanssupporting said pinion including bearings on both sides of said rack barsupporting said pinion, at least one of said bearings eccentricallymounted in said housing, the eccentric distance between the centerlineof the one bearing and the centerline of the pinion lying in a planeparallel to the centerline of the rack, the eccentrically mountedbearing being a spherical bearing having a spherical outer surfacereceived in an opening in a mounting member, said mounting member havinga cylindrical outer diameter surface rotatably received in a cylindricalportion of the housing, said opening in the said mounting membereccentric to the cylindrical outer diameter of the mounting member, saidmounting member rotatable in said housing, and means restrictingrotation of said mounting member.
 2. The assembly of claim 1 whereinanother of said bearings having a spherical outer surface received in amating mounting member supports the pinion in the housing on theopposite side of the rack bar from the one of said bearings.